Guide device for welding curvilinear pipe surfaces

ABSTRACT

Guide device for use in the processing, in particular welding, of curved surfaces, in particular pipe surfaces. A guide device includes a flexible elongate body provided with a guide for processing means and a tensioning means for tensioning the flexible body around the curved surface. The flexible body is provided along its length with indicators arranged according to a determined pattern, this pattern being such that a determined position of the guide device along the flexible body can be inferred on the basis of the detection of the indicators.

The present invention relates to a guide device for use in theprocessing, in particular welding, of curved surfaces, in particularpipe surfaces, and more in particular pipelines. Such a guide devicegenerally comprises a flexible elongate body provided with a guide forprocessing means, and tensioning means for tensioning the flexible bodyaround the curved surface. The invention further relates to a method forwelding a pipeline in a number of welding passes making use of such aguide device.

In the welding of pipelines it is known to use a guide band along whicha carriage with one or more welding torches is guided. In the laying ofpipelines at sea a number of welding steps must generally take place onboard ship, these welding steps taking place in different weldingstations. According to the known systems an operative of a weldingstation will indicate on the pipe, for instance using chalk asindicator, the point to which the welding layer has been deposited. Theoperative of a subsequent welding station must then search for thislocation and, from this location, carry out a following welding step inwhich a subsequent welding layer is deposited. Such a working methodslows down the welding process and impedes automation thereof.

The present invention has for its object to provide a guide device ofthe type stated in the preamble with which a location along the guidedevice can be determined in a manner which is simple and can beautomated. The guide device is distinguished for this purpose in thatthe flexible body is provided along its length with indicators arrangedaccording to a determined pattern, this pattern being such that adetermined position along the flexible body can be inferred on the basisof the detection of the indicators.

In this manner a location on the flexible body can thus be determinedwith sufficient accuracy on the basis of the pattern of indicatorsarranged on the flexible body. The location can thus be exactlydetermined at the end of a welding step, and this location can onceagain be searched for prior to a subsequent welding step.

A sensor adapted to detect these indicators and a signal processing unitconnected to the sensor for determining a location along the flexiblebody on the basis of the detected indicators are preferably provided. Inthis away a determined location along the guide band can be determinedfor further use in a manner which is simple and can be automated.

According to the preferred embodiment the indicators are holes. Thepattern can for instance consist of at least one row of indicatorsarranged in the lengthwise direction of the flexible body, wherein themutual distance between adjacent indicators gradually increases. This isa simple pattern which is easy to detect.

According to the preferred embodiment, the pattern comprises a first rowof indicators and a second row of indicators parallel thereto, whereinthe mutual distance between adjacent indicators of the first and secondrow increases in opposite directions. In this way the same pattern isseen by the sensor irrespective of the manner in which the guide deviceis arranged on the curved surface (for instance clockwise orcounter-clockwise in the case of a pipe surface).

The flexible body is preferably further a metal band, and the indicatorsare preferably formed by punching holes.

According to a possible embodiment, the metal band has a serrated edge.Such an edge enables the driving of the carriage of the processing meansby means of a drive wheel which engages on this edge.

In the case of a guide band arranged around a pipe surface it can be offurther importance that it be properly centered and can be arranged witha fixed peripheral length around the pipe surface. This fixed peripherallength is particularly useful when operation takes place with indicatorsin order to enable detection of the same pattern along the periphery atall times.

Guide bands exist wherein spacers are arranged between the guide bandand the pipe surface. Spring means can be arranged therein. However,such spacers typically extend over the full width of the guide band.This has the drawback that the friction between the spacers and the pipesurface on which the guide band is mounted is quite high, which canresult in an asymmetrical, non-centered arrangement of the guide bandaround the pipe surface, wherein the springs are more compressed on oneside than on the other.

In order to solve this problem the invention further proposes a guidedevice as described in claims 15 to 18. By ensuring that the width andlength dimensions of the contact surface between each spacer and thepipe surface are small relative to the dimensions of the guide band thefriction is limited to a minimum and the guide band can be arrangedproperly centered around a pipe surface, wherein the spring means areall compressed in a substantially uniform manner.

According to an advantageous embodiment, each spacer comprises a springcarrier which is connected to the guide band and a spring holderarranged in spring-mounted manner therearound, wherein the spring meansare preferably cup springs acting between the spring carrier and thespring holder. This embodiment will be described further with referenceto the figures.

The present invention further relates to a flexible body for use in adevice according to the invention.

The present invention also relates to a method for welding a pipeline ina number of welding passes making use of a device according to theinvention, wherein a first layer is deposited during a first weldingpass and a second layer is deposited in a subsequent welding pass. Themethod is distinguished in that

-   the final location of the welding layer is determined on the basis    of the indicators after depositing of the first layer;-   this final location is searched for on the basis of the indicators    on the guide band prior to depositing of the second layer.

Such a method thus allows further automation of the welding process.

Above-mentioned and other features will be further elucidatedhereinbelow on the basis of an exemplary embodiment of the guide deviceaccording to the invention which is described with reference to theaccompanying drawings. In the drawings:

FIG. 1 shows a detail of an embodiment of the guide band according tothe invention arranged around a pipe surface, with a welding torch asprocessing member;

FIG. 2 shows a perspective view of an embodiment of the guide bandaccording to the invention;

FIG. 3A is a top view of the tensioning means of the guide band of FIG.2;

FIG. 3B shows a cross-section along line B-B in FIG. 3A;

FIG. 3C shows a cross-section along line C-C in FIG. 3A;

FIG. 3D shows a cross-section along line D-D in FIG. 3A;

FIG. 4 is a top view of the embodiment of the guide band of FIG. 3 indetached situation;

FIG. 5 is a detail of the edge of the guide band shown in FIG. 4;

FIGS. 6A and 6B show respectively a top view and cross-section alongline VI-VI of FIG. 6A of a first part of a spacer;

FIGS. 7A and 7B show respectively a top view and cross-section alongline VII-VII of FIG. 7A of a second part of a spacer.

FIG. 1 shows schematically a device for welding together pipes B whichmust be welded to each other on their end edges. The end edges aretypically formed such that a weld groove L is created when the pipes areplaced against each other.

Such weld grooves are generally filled in multiple passes of the weldingtorch, wherein one layer of the welding material at a time is depositedin the groove. One or more welding torches 1 can be used for thispurpose. The welding torch is supported by a carriage 2 guided along aguide band fastened around one of the pipe ends. In the shown embodimentwelding torch 1 is connected to a flexible feed pipe 35 for a protectivegas, although this is not a prerequisite and depends on the weldingtechnique used. The welding device is assumed known per se and does notform part of the invention.

Carriage 2 is provided with four guide wheels 22 which have a U-shapedperipheral surface in which the guide edge 24 of guide band 3 isreceived. By biasing the opposite guide wheels 22 toward each other, forinstance with a spiral spring assembly 25, the pair of wheels is heldand pressed firmly against the sides of guide band 3. The driving ofcarriage 2 along guide band 3 can take place in random manner. In theshown embodiment the driving is performed by means of a drive wheel 26which engages on the side edge of the guide band and is driven by adrive mechanism (not shown). Such a carriage is assumed known and willnot be elucidated in more detail here.

FIG. 2 is a perspective view showing an embodiment of guide band 3according to the invention in a situation where it is formed into aring. FIG. 4 shows a top view of the guide band in the extended state.The guide band is provided on its inner side with spacers 7 in whichspring means 10 are arranged. Tensioning means are provided betweenouter ends 5, 6 and guide band 3 for the tensioning as a ring around thepipe surface. Tensioning means 4 are shown in more detail in FIGS.3A-3D. A first element 13 of the tensioning means is fastened to outerend 6 using four screws 16. This first element 13 is provided with athreaded bore 14. The second element 15 is fastened to the other outerend 5 using four screws 16. This element is provided with an elongatedcavity 17 for placing therethrough of a screw which is tightened inthreaded bore 14.

Guide band 3 is further provided with indicators which are arranged inaccordance with a determined pattern and which here take the form ofholes 8, 8′. The pattern consists here of two sequences of square holes.The first sequence is a number of square holes 8 which are arranged on aperipheral line, wherein the mutual distance between two adjacent holesgradually increases running from outer end 6 to outer end 5. The secondsequence is likewise formed by a number of square holes 8′ arranged on aperipheral line, wherein the mutual distance between two adjacent holesgradually decreases running from outer end 6 to outer end 5. Thisgradual increase/decrease is identical for both sequences such that inthe case of reverse arrangement of the guide belt, i.e. when outer ends5 and 6 are interchanged, an identical pattern is obtained.

A sensor 36 for detecting this pattern is provided in carriage 2, asschematically illustrated in FIG. 1. This sensor is coupled to a signalprocessing unit 37 (schematically shown in FIG. 1) adapted to determinethe location along the guide belt on the basis of the holes along whichthe carriage passes and which are detected by the sensor.

During laying of pipelines four to five welding steps must generallytake place on the ship, wherein after each welding step the ship travelsa determined distance, whereby the weld is carried to the followingwelding station and the following welding step can be performed. Usingthe indicators on the guide band and the sensor the final location ofthe weld is determined after each welding step and transmitted to thefollowing welding station. In the following welding station the weldingtorch is carried once again to this location using the indicators andthe sensor such that the welding step begins exactly at the positionwhere the previous welding step was ended. Very precise welding can thusbe carried out in this way.

A possible embodiment of the spacer with spring means will now bedescribed in detail with reference to FIGS. 3A-3D and FIGS. 6A-6B and7A-7B. Spacer 7 comprises a spring holder 31 and a spring carrier 30accommodated therein. Spring carrier 30 is connected to the guide bandusing a screw 38. Spring holder 31 has limited movement in the directionof the guide band. This is realized by providing spring holder 31 withan opening 35 having dimensions which are such that spring holder 31 canmove along the periphery of spring carrier 30 in the direction of theguide band. The freedom of movement is herein adjustable by means of ascrew 37 (see FIG. 3B) which protrudes through opening 35 of springholder 31 and is screwed fixedly into a threaded bore 36 in springholder 30. Spring means 10 act between spring carrier 30 and springholder 31. The form of spring carrier 30 and that of spring holder 31must therefore be adapted to each other such that spring means can beaccommodated in spring holder 31 on the one hand and that spring holder31 has limited movement relative to spring carrier 30 on the other. Inthe shown embodiment spring holder 31 is substantially cup-shaped with abottom 37 provided with an opening 35, and with a cylindrical wall 34.Spring carrier 30 here takes the form of a hollow cylinder 32 in whichscrew thread is provided and the top end of which is provided with aradially oriented collar 33. The skilled person will however appreciatethat other forms are possible for spring holder 31 and spring carrier30.

In addition, the contact surface between the spring holder and thecurved surface on which the guide band is mounted must preferably be assmall as possible in order to limit the friction with the curvedsurface. To this end spring holder 31 preferably has a rounded bottom,as can best be seen in FIG. 7B, and the surface area of the annularsupport surface is preferably as small as possible.

The invention is not limited to the above described embodiment, andcertainly not to the processing of pipelines. Any surface on which aflexible guide band can be mounted in suitable manner falls within thescope of the invention. The skilled person will further appreciate thatmany different patterns of indicators are possible. The scope ofprotection of the present invention is therefore defined solely by theappended claims.

The invention claimed is:
 1. Guide device for guiding a welding carriagefor welding a pipe surface, said guide device comprising: a weldingcarriage comprising a sensor; a metal band provided with a guide for thewelding carriage; said metal band having a length; and a tensioner fortensioning the metal band around the pipe surface; wherein the metalband is provided along the length thereof with indicators arrangedaccording to a determined pattern; and wherein said sensor is configuredto move relative to the indictors, and to optically detect a portion ofthe determined pattern represented by one or more of said indicators,said portion of the determined pattern being such that a determinedposition along the metal band is inferred based on a detection of saidindicators by said sensor when the welding carriage and sensor arestationary with respect to the metal band, wherein the portion of thedetermined pattern detected by the sensor allows a unique location ofthe welding carriage on the metal band to be determined; wherein saidmetal band has a first outer end and a second outer end, wherein theindicators arranged according to the determined pattern comprise atleast one row of indicators; wherein said at least one row of indicatorsextends between said first outer end and said second outer end; andwherein adjacent indicators of said at least one row of indicators beingspaced apart by a mutual distance, said mutual distance graduallyincreasing from said first outer end to said second outer end.
 2. Guidedevice as claimed in claim 1, further comprising a signal processingunit connected to the sensor for inferring a position along the metalband on the basis of the detected indicators.
 3. Guide device as claimedin claim 1, wherein the indicators are holes.
 4. Guide device as claimedin claim 1, further comprising a second row of indicators parallel thefirst row of indicators; said first row of indicators and said secondrow of indicators extending between said first outer end and said secondouter end; wherein adjacent indicators of said first row being spacedapart by a first mutual distance which increases from said first outerend to said second outer end; and adjacent indicators of said second rowbeing spaced apart at a second mutual distance which increases from saidsecond outer end to said first outer end.
 5. Guide device as claimed inclaim 1, wherein the indicators arranged according to the determinedpattern are holes in said metal band.
 6. Guide device as claimed inclaim 1, wherein the metal band is provided on its underside withspacers.
 7. Guide device as claimed in claim 6, wherein the spacers areprovided with spring means.
 8. Guide device as claimed in claim 7,wherein said spacer comprises a cup-shaped spring holder, having a firstopen end directed towards the metal band and a second end remote fromthe metal band in the form of an annular support foot for making contactwith the pipe surface; said spring means being provided in the cupshaped spring holder; and acting between the spring holder and the metalband.
 9. Guide device as claimed in claim 8, said metal band being aguide band having width and length dimensions, wherein said width andlength dimensions of said contact surface are small relative to saidwidth and length dimensions of the guide band.
 10. Guide device asclaimed in claim 1, wherein the metal band has a serrated edge for thepurpose of forming guiding for the welding carriage.